detent

hammas That which locks or unlocks a movement; a catch, pawl, or dog; especially, in clockwork, the catch which locks and unlocks the wheelwork in striking.
1972, Mayer et al., United States Patent 3760640, abstract:

A UHF tuner having 70 detent positions with fine tuning capability at all locations. Coarse tuning is accomplished via a toothed, detented disk and a spirally-extending rim having a follower lever operable therewith.